All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Intravaginal rings, sub-dermal implants, and pessaries/suppositories are routinely used for the delivery of drugs both topically and systemically to vaginal or rectal tissue. Typically, these devices are made from a polymer matrix such as silicone, and the drug is dispersed throughout the matrix. Release of the drug occurs by diffusion of the drug molecules through the polymer matrix and partitioning into the fluid in the area of the body where the device is placed (e.g., in the vaginal fluid for an intravaginal ring). Two examples of matrix release devices are the intravaginal ring products Nuvaring, for the delivery of contraceptive hormones, and Estring, for the delivery of estradiol for hormone replacement therapy in menopausal women. Matrix devices provide limited control of drug release rate because the release is controlled exclusively by two factors: the relative partitioning of the drug between the polymer matrix material and the fluid into which it is released, and the diffusional characteristics of the drug within the polymer matrix. Accordingly, there exists a need in the art for drug delivery devices that allow for more control over the release of the drugs.